In ectothermic organisms, temperature plays a vital role in survival and reproductive success. Founding isofemale lines from wild-collected females is a basic tool for characterizing quantitative traits in a natural population. The effects of heat shock, i.e., short exposure to heat stress, on survival and reproductive success in 10 recently collected isofemale lines of Drosophila ananassae Doleschall, 1858 were compared. Flies were treated as follows: (i) unstressed control; (ii) placed at 37 deg Cfor 90 min (pre-treatment); (iii) placed at 40 deg C for 60 min 24 h before the fecundity test; and (iv) placed at 40 deg C for 60 min with pre-treatment 16 h before they were exposed to 40 deg C. The heat stress strongly affected survival. However, there was no significant difference between the survival of males and females. Furthermore, the female fecundity, measured as F_1 offspring produced over the next 12 days, was also reduced. Heat pre-treatment improved survival of both male and female and also improved female productivity. We found significant variation in female fecundity among isofemale lines, and intraclass correlations increased for stress treatments. The results suggest that a small increase in environmental stress may affect fitness traits, and there is enough genetic variation for thermal adaptation in D. ananassae.
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